JP6496475B2 - Power conversion system - Google Patents

Description

  Embodiments of the present invention generally relate to a power conversion system, and more specifically to a power conversion system used in an electric vehicle or the like.

  In recent years, there has been a lot of research focusing on measures against environmental pollution and fossil fuel depletion. Specifically, the automotive industry has concentrated its efforts on research on electric vehicles (EVs) that use batteries as their primary energy source. Generally, EV systems require a power conversion system that is used to transfer energy from the battery to a drive motor for driving the electric vehicle.

  For example, FIG. 1 shows a conventional power conversion system 10 for an electric vehicle. The power conversion system 10 may include a battery 11, a drive motor 12, a DC / DC converter 13, a three-phase inverter 14, a DC link 15 including a capacitor C1, a filter unit 16, and a control unit 17. The DC / DC converter 13 is used for boosting the DC voltage of the battery 11 and is electrically coupled to the battery 11 via the filter unit 16. The inverter 14 is used to convert the boosted DC voltage from the converter 13 into a three-phase AC voltage via the DC link 15. The drive motor 12 receives the converted three-phase AC voltage from the inverter 14 to drive the electric vehicle. The control unit 17 is used to supply a pulse width modulation (PWM) command to the converter 13 and the inverter 14 in order to appropriately convert the DC voltage into a three-phase AC voltage.

  In order to implement voltage conversion, the converter 13 and the inverter 14 may each include a plurality of switch elements such as 12 switch elements S1 to S12 controlled by the PWM command of the control unit 17. In the conventional power conversion system 10, these switch elements S1-S12 may include transistors such as silicon insulated gate bipolar transistors (IGBTs). However, the conventional silicon IGBTs S1-S12 can consume a lot of energy during the energy transfer process, which reduces efficiency. On the other hand, because of the silicon IGBTs S1 to S12 that generate a lot of heat, it is necessary to arrange a heat sink (not shown) on the silicon IGBTs S1 to S12. This requires additional space and increases the weight of the electric vehicle, which in turn reduces its power density and performance.

  Furthermore, to achieve multiple phases of voltage, the filter unit 16 may include multiple inductors such as three interleaved inductors L1, L2, and L3. However, these inductors L1, L2 and L3 may require additional space in the electric vehicle as well.

In addition, in order to control these switch elements S1-S12, the control unit 17 should provide appropriate PWM commands. For example, FIG. 2 shows a control schematic diagram of the control unit 17 for controlling the DC / DC converter 13. The control unit 17 may include a difference element 171 and a PWM command generation block 172. The difference element 171 is used to obtain a DC voltage error signal V _{DC # Err} calculated from the difference between the feedback DC voltage signal V _{DC # Fbk} on the capacitor C1 and a predetermined DC voltage command signal V _{DC # cmd.} Is done. The PWM command generation block 172 is used to generate an appropriate PWM command (PWM_cmd) according to the DC voltage error signal V _{DC # Err} . The feedback DC voltage signal V _{DC # Fbk} represents the actual measured voltage on the capacitor C1, and the predetermined DC voltage command signal V _{DC # cmd} represents the predetermined DC voltage.

It should be understood that the PWM command generation block 172 may include a number of calculation elements, such as proportional-integral regulators, limiters, difference elements, comparators, etc., to calculate the PWM command (PWM_cmd). In the conventional control unit 17, the predetermined DC voltage command signal V _{DC # cmd} has a constant voltage value (see FIG. 2). However, the predetermined DC voltage command signal V _{DC # cmd} has a constant voltage value, and the DC / DC converter 13 outputs DC power while the inverter 14 outputs AC power. Should have enough capacitance to handle the pulsating power.

  For these and other reasons, there is a need for embodiments of the present invention.

  According to one embodiment disclosed herein, a power conversion system is provided. The power conversion system includes a filter unit, a DC / DC converter, a DC link, an inverter, a control unit, and a drive motor. The DC / DC converter is used for boosting the DC voltage of the DC power supply and is electrically coupled to the DC power supply through the filter unit. The DC / DC converter includes a plurality of SiC MOSFETs configured in a synchronous rectification mode by channel reverse conduction control. The inverter is used to convert the boosted DC voltage from the converter into a multiphase AC voltage via a DC link. The control unit is used to supply PWM commands to the converter and the inverter to convert the DC voltage into an AC voltage configured to drive an AC driven device.

  These and other features, aspects, and advantages of the present invention will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like numerals represent like parts throughout the drawings, wherein: .

It is the schematic of the conventional power conversion system of an electric vehicle. FIG. 2 is a control schematic diagram of a control unit of the conventional power conversion system of FIG. 1 for controlling a DC / DC converter. 1 is a schematic diagram of an electric vehicle power conversion system according to an embodiment. FIG. It is the schematic of the power conversion system of the electric vehicle by other embodiment. FIG. 5 is a schematic diagram of three magnetically coupled inductors of the power conversion system of FIG. 4 according to one embodiment. FIG. 5 is a schematic diagram of three magnetically coupled inductors of the power conversion system of FIG. 4 according to another embodiment. FIG. 4 is a control schematic diagram of a control unit of the power conversion system of FIG. 3 for controlling a DC / DC converter according to an embodiment.

  Embodiments described herein relate generally to a power conversion system. The power conversion system includes a filter unit, a DC / DC converter, a DC link, an inverter, a control unit, and a drive motor. The DC / DC converter is used for boosting the DC voltage of the DC power supply and is electrically coupled to the DC power supply through the filter unit. The DC / DC converter includes a plurality of SiC MOSFETs configured in a synchronous rectification mode by channel reverse conduction control. The inverter is used to convert the boosted DC voltage from the converter into a multiphase AC voltage via a DC link. The control unit is used to supply PWM commands to the converter and the inverter to convert the DC voltage into an AC voltage configured to drive an AC driven device.

  Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. As used herein, the terms “first”, “second”, etc. do not indicate any order, quantity, or importance, but are used to distinguish one element from another. Is done. Also, the term “one” does not indicate a quantity limitation and indicates the presence of at least one such item, and terms such as “front”, “back”, “bottom”, and / or “top” Unless stated otherwise, it is used merely for convenience of explanation and is not limited to any one location or spatial orientation. Furthermore, the terms “coupled” and “connected” are not intended to distinguish between direct or indirect coupling / connection between two components. Rather, such components may be coupled / connected directly or indirectly unless otherwise specified.

  Referring to FIG. 3, an electric vehicle power conversion system 20 according to an embodiment is shown. In the illustrated embodiment, the power conversion system 20 includes a DC power source 21, an AC drive type device 22, a three-phase DC / DC converter 23, a three-phase inverter 24, a DC link 25 including a capacitor C1, A filter unit 26 and a control unit 27 are included. The filter unit 26 includes three inductors L1, L2 and L3 connected in an interleaved manner. The DC / DC converter 23 is used to boost the DC voltage of the DC power supply 21 and is electrically coupled to the DC power supply 21 via the filter unit 26. In one embodiment, the DC power source 21 represents a battery. The inverter 24 is used to convert the boosted DC voltage from the converter 23 into a three-phase AC voltage via the DC link 25. The AC drive type device 22 receives the three-phase AC voltage converted from the inverter 24. In one embodiment, AC drive type device 22 is a drive motor that receives a three-phase AC voltage converted from inverter 24 to drive an electric vehicle. The control unit 27 is used to supply a PWM command to the converter 23 and the inverter 24 in order to appropriately convert the DC voltage into a three-phase AC voltage. In other embodiments, the number of phases of inverter 24 and converter 23 may vary if desired. Although the power conversion system 20 is described herein as being used in an electric vehicle, the power conversion system 20 can also be used in other devices that need to be driven by AC power. Further, although the illustrated embodiment of the power conversion system 20 includes a DC power supply 21 and an AC driven device 22 for completeness, the power conversion system 20 need not be required to include these elements. .

  In order to implement the voltage conversion, the converter 23 and the inverter 24 each include a plurality of switch elements, such as 12 switch elements S1 'to S12' controlled by the PWM command of the control unit 27. In the power conversion system 20, these switch elements S1'-S12 'include transistors such as silicon carbide (SiC) metal oxide field effect transistors (MOSFETs). Since the SiC MOSFETs S1 ′ to S12 ′ have a synchronous rectification (SR) mode with channel reverse conduction control, they operate current through the SiC MOSFETs S1 ′ to S12 ′ along the channel with low loss. Can do. That is, each of the SiC MOSFETs S1 ′ to S12 ′ can be made to have inverted channel conduction from the source terminal to the drain terminal by a positive gate drive signal to the gate terminals of the SiC MOSFETs S1 ′ to S12 ′. This can create a current path through the low loss channel. Therefore, compared to the conventional power conversion system 10 of FIG. 1, the SiC MOSFETs S1'-S12 'consume less energy during the energy transfer process. Therefore, the energy transfer efficiency of the power conversion system 20 is increased by using the SiC MOSFETs S1 'to S12' instead of the conventional IGBTs S1 to S12.

  Furthermore, because the SiC MOSFETs S1 'to S12' consume less energy, the heat generated by the SiC MOSFETs S1 'to S12' is less than the heat generated by the conventional IGBTs S1 to S12. Therefore, the number or volume of heat sinks (not shown) arranged on the SiC MOSFETs S1 'to S12' is smaller than the number or volume of heat sinks arranged on the IGBTs S1 to S12 of FIG.

  Referring to FIG. 4, an electric vehicle power conversion system 20 according to another embodiment is shown. Compared with the embodiment of FIG. 3, this embodiment of FIG. 4 replaces three individual inductors L1, L2 and L3 with three magnetically coupled inductors La, Lb and Lc. The individual inductors L1, L2, and L3 each include an individual magnetic core and a coil (not shown) wound around the magnetic core, so the total number of magnetic cores of the individual inductors L1, L2, and L3 is three. It is. However, the three magnetically coupled inductors La, Lb and Lc share a common magnetic core together, which can save physical space in the circuit. Furthermore, the common mode circulating current is suppressed by the coupling coefficient of the three magnetically coupled inductors La, Lb and Lc, and the magnetically coupled inductors La, Lb and Lc are divided into three individual inductors L1, Compared to L2 and L3, the internal loop circulating current can be suppressed, which can further reduce the loss. In the following paragraphs, two detailed embodiments of three magnetically coupled inductors La, Lb and Lc are described.

  Referring to FIG. 5, a schematic diagram of three magnetically coupled inductors La, Lb and Lc of the power conversion system 20 of FIG. 4 according to one embodiment is shown. In this embodiment, the three magnetically coupled inductors La, Lb and Lc include a shared magnetic core 262 and three coils ‘a’, ‘b’ and ‘c’. Shared magnetic core 262 includes three parallel magnetic pillars 2622, 2624 and 2626 that are electrically coupled together. Three coils 'a', 'b' and 'c' are wound around three parallel magnetic columns 2622, 2624 and 2626, respectively. In other embodiments, the number of coils and magnetic columns may vary based on the number of phases of converter 23 and inverter 24.

  Referring to FIG. 6, a schematic diagram of three magnetically coupled inductors La, Lb and Lc of the power conversion system 20 of FIG. 4 according to another embodiment is shown. This embodiment includes a shared magnetic core 264 and three coils 'a', 'b' and 'c'. The shared magnetic core 264 has a ring shape. The three coils ‘a’, ‘b’, and ‘c’ are each equally wound around three different portions of the ring-shaped magnetic core 264. The turn ratio of the three coils ‘a’, ‘b’ and ‘c’ is 1: 1: 1. Although two embodiments of three magnetically coupled inductors La, Lb and Lc are shown, the shared magnetic core can be varied as required without departing from the spirit and scope of the claimed invention. Good. In other embodiments, the number of magnetically coupled inductors can be varied depending on the number of phases of the output voltage. For example, a five phase output voltage can utilize five magnetically coupled inductors by using similar circuit connections as described above.

Referring to FIG. 7, a control schematic diagram of the control unit 27 of the power conversion system 20 of FIG. 3 for controlling the DC / DC converter 23 according to one embodiment is shown. In at least some embodiments, the control unit 27 includes a difference element 271 and a PWM command generation block 272. The difference element 271 obtains a DC voltage error signal V ′ _{DC # Err} calculated from a difference between the feedback DC voltage signal V ′ _{DC # Fbk} on the capacitor C1 and a predetermined DC voltage command signal V ′ _{DC # cmd.} Used for. The PWM command generation block 272 is used to generate an appropriate PWM command (PWM_cmd) according to the DC voltage error signal V ′ _{DC # Err} . The feedback DC voltage signal V ′ _{DC # Fbk} represents the actual measured voltage on the capacitor C1, and the predetermined DC voltage command signal V ′ _{DC # cmd} represents the predetermined DC voltage.

It should be understood that the PWM command generation block 272 may include a number of computing elements, such as proportional-integral regulators, limiters, difference elements, comparators, etc., to calculate the PWM command (PWM_cmd). Compared with the conventional predetermined DC voltage command signal V _{DC # cmd of} FIG. 2, the predetermined DC voltage command signal V ′ _{DC # cmd} is an active pulsating DC voltage signal (see FIG. 7). The frequency of the pulsating DC voltage signal V ′ _{DC # cmd} matches the frequency of the AC voltage signal to be converted by the inverter 24. For example, the pulsating DC voltage signal V ′ _{DC # cmd} may be a sine wave. Since the predetermined DC voltage command signal V ′ _{DC # cmd} provides active voltage pulsation control with the same frequency of the converted AC voltage, the capacitor C1 is a capacitor used in the conventional power conversion system 20. Compared to C1, it takes on less energy conversion function from DC to AC. This in turn reduces the capacitance of the capacitor C1 of the power conversion system 20.

  Although the invention has been described with reference to exemplary embodiments, it should be understood that various changes can be made and equivalents can be substituted for the elements without departing from the scope of the invention. It will be understood by the vendor. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Accordingly, the invention is not limited to the specific embodiments disclosed as the best mode contemplated for carrying out the invention, but the invention is intended to cover all claims within the scope of the appended claims. Embodiments will be included.

  It should be understood that not all such objects and advantages described above may be achieved by any particular embodiment. Thus, for example, those skilled in the art will appreciate that the systems and techniques described herein may be taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein. It will be understood that this may be implemented or carried out in a manner that achieves or optimizes a single advantage or group of advantages.

DESCRIPTION OF SYMBOLS 10 Power conversion system 11 Battery 12 Drive motor 13 DC / DC converter 14 Three-phase inverter 15 DC link 16 Filter unit 17 Control unit 20 Power conversion system 21 DC power supply 22 AC drive type device 23 Three-phase DC / DC converter 24 Three-phase inverter 25 DC link 26 Filter unit 27 Control unit 171 Difference element 172 PWM command generation block 262 Shared magnetic core 264 Shared magnetic core 271 Difference element 272 PWM command generation block 2622 Parallel magnetic column 2624 Parallel magnetic column 2626 Parallel magnetic column a to c Coil C1 Capacitor L1 to L3 Inductor La to Lc Inductor S1 to S12 Switch element S1 ′ to S12 ′ Switch element

Claims (13)

A filter unit;
A multi-phase DC / DC converter for boosting a DC voltage of a DC power supply, wherein the plurality of DC / DC converters are electrically coupled to the DC power supply via the filter unit and configured in a synchronous rectification mode by channel reverse conduction control. A silicon carbide (SiC) metal oxide semiconductor field effect transistor (MOSFET), and a positive gate drive signal supplied to the gate terminals of the plurality of SiC MOSFETs causes each of the plurality of SiC MOSFETs to A multi-phase DC / DC converter, with inverted channel conduction to the drain terminal;
DC link,
An inverter for converting the boosted DC voltage from the DC / DC converter into a multiphase AC voltage for driving an AC drive type device via the DC link;
A control unit that supplies a pulse width modulation (PWM) command to the DC / DC converter and the inverter, and the command to the DC / DC converter and the PWM command to the inverter have the same frequency. , Power conversion system. The power conversion system according to claim 1, wherein the inverter includes a plurality of SiC MOSFETs configured in a synchronous rectification mode by channel reverse conduction control. The power conversion system according to claim 1, wherein the inverter is a multiphase inverter. The power conversion system according to claim 1, wherein the filter unit includes a plurality of magnetically coupled inductors. The power conversion system according to claim 4, wherein the plurality of magnetically coupled inductors include a shared magnetic core and a plurality of windings wound around the shared magnetic core. The shared magnetic core includes a plurality of parallel magnetic columns and a plurality of coils that are electrically coupled to each other, and each of the plurality of coils is wound around the plurality of parallel magnetic columns. Power conversion system. The power conversion system according to claim 6, wherein the shared magnetic core has a ring shape, and the plurality of coils are wound around three different portions of the shared magnetic core that are equally ring-shaped. The power conversion system according to claim 7, wherein a turn ratio of the plurality of coils is one. The control unit is
A difference element for obtaining a DC voltage error signal calculated from a difference between a feedback DC voltage signal on the DC link and a predetermined DC voltage command signal, wherein the predetermined DC voltage command signal is A differential element comprising an active pulsating DC voltage signal, wherein the frequency of the pulsating DC voltage signal matches the frequency of the AC voltage to be converted by the inverter;
The power conversion system according to claim 1, further comprising: a PWM command generation block for generating a PWM command according to the DC voltage error signal. The power conversion system of claim 9, wherein the predetermined DC voltage command signal includes a sine wave signal. The power conversion system according to claim 9 or 10, wherein the DC link includes a capacitor. The power conversion system according to claim 9, wherein the filter unit includes a plurality of magnetically coupled inductors. The power conversion system according to any one of claims 1 to 12, wherein the DC power source includes a battery, and the AC drive type device includes a drive motor used in an electric vehicle.